Star Pupil

Star Pupil enters with a +1/+1 counter on it.
When Star Pupil dies, put its counters on target creature you control.

Lightwalker

Lightwalker has flying as long as it has a +1/+1 counter on it.

Battlefield Promotion

Put a +1/+1 counter on target creature. That creature gains first strike until end of turn. You gain 2 life. (A creature with first strike deals combat damage before creatures without first strike.)

Basri's Acolyte

Lifelink (Damage dealt by this creature also causes you to gain that much life.)
When Basri's Acolyte enters, put a +1/+1 counter on each of up to two other target creatures you control.

Plains

Patron of the Valiant

Flying
When Patron of the Valiant enters, put a +1/+1 counter on each creature you control with a +1/+1 counter on it.

Basri's Solidarity

Put a +1/+1 counter on each creature you control.

Steadfast Sentry

Vigilance (Attacking doesn't cause this creature to tap.)
When Steadfast Sentry dies, put a +1/+1 counter on target creature you control.

Cave of Temptation

{T}: Add {C}.
{1}, {T}: Add one mana of any color.
{4}, {T}, Sacrifice Cave of Temptation: Put two +1/+1 counters on target creature. Activate only as a sorcery.

Basri's Lieutenant

Vigilance, protection from multicolored
When Basri's Lieutenant enters, put a +1/+1 counter on target creature you control.
Whenever Basri's Lieutenant or another creature you control dies, if it had a +1/+1 counter on it, create a 2/2 white Knight creature token with vigilance.

Banishing Light

When this enchantment enters, exile target nonland permanent an opponent controls until this enchantment leaves the battlefield.

Swift Response

Urdnan, Dromoka Warrior

When Urdnan, Dromoka Warrior enters, put a +1/+1 counter on target creature.
Whenever you attack, target attacking creature with a +1/+1 counter on it gains first strike until end of turn. If that creature has two or more +1/+1 counters on it, it gains double strike until end of turn instead.

Thriving Heath

Thriving Heath enters tapped. As it enters, choose a color other than white.
{T}: Add {W} or one mana of the chosen color.

Sandsteppe Outcast

When Sandsteppe Outcast enters, choose one —
• Put a +1/+1 counter on Sandsteppe Outcast.
• Create a 1/1 white Spirit creature token with flying.